Polyolefin production

ABSTRACT

Use of metallocene catalyst component for the preparation of a syndiotactic polyolefin having a monomer length of up to C10, which component has the general formula: R″(C p R 1 R 2 )(C p ′R 1 ′R 2 ′)MQ 2  wherein C p  is a cyclopentadienyl ring; C p ′ is a 3,6 disubstituted fluorenyl ring; R 1  and R 2  are each independently H or a substituent on the cyclopentadienyl ring which is proximal to the bridge, which proximal substituent is linear hydrocarbyl of from 1 to 20 carbon atoms or a group of the formula XR* 3  containing up to 7 carbon atoms in which X is chosen from Group IVA, and R* is the same or different and chosen from hydrogen or alkyl; R 1 ′ and R 2 ′ are each independently substituent groups on the fluorenyl ring, each of which is a group of the formula AR′″ 3 , in which A is chosen from Group IVA, and each R′″ is independently hydrogen or a hydrocarbyl having 1 to 20 carbon atoms; M is a Group IVB transition metal or vanadium; each Q is hydrocarbyl having 1 to 20 carbon atoms or is a halogen; R″ is a structural bridge imparting stereorigidity to the component and comprises the moiety TR a R b , in which T is chosen from group IVA, and each of R a  and R b  is independently (i) substituted or unsubstituted aryl linked to T directly or by C 1 -C 4  alkylene; or (ii) H.

FIELD OF THE INVENTION

The present invention relates to a metallocene catalyst component foruse in preparing polyolefins, especially polypropylenes. The inventionfurther relates to a catalyst system which incorporates the metallocenecatalyst component and a process for preparing such polyolefins.

BACKGROUND TO THE INVENTION

Olefins having 3 or more carbon atoms can be; polymerised to produce apolymer with an isotactic stereochemical configuration. For example, inthe polymerisation of propylene to form polypropylene, the isotacticstructure is typically described as having methyl groups attached to thetertiary carbon atoms of successive monomeric units on the same side ofa hypothetical plane through the main chain of the polymer. This can bedescribed using the Fischer projection formula as follows:

Another way of describing the structure is through the use of NMRspectroscopy. Bovey's NMR nomenclature for an isotactic pentad is . . .mmmm with each “m” representing a “meso” diad or successive methylgroups on the same side in the plane.

In contrast to the isotactic structure, syndiotactic polymers are thosein which the methyl groups attached to the tertiary carbon atoms ofsuccessive monomeric units in the chain lie on alternate sides of theplane of the polymer. Using the Fischer projection formula, thestructure of a syndiotactic polymer is described as follows:

In NMR nomenclature, a syndiotactic pentad is described as . . . rrrr .. . in which “r” represents a “racemic” diad with successive methylgroups on alternate sides of the plane.

In contrast to isotactic and syndiotactic polymers, an atactic polymerexhibits no regular order of repeating unit. Unlike syndiotactic orisotactic polymers, an atactic polymer is not crystalline and formsessentially a waxy product.

While it is possible for a catalyst to produce all three types ofpolymer, it is desirable for a catalyst to produce predominantly anisotactic or syndiotactic polymer with very little atactic polymer.

EP-A-0426644 relates to syndiotactic copolymers of olefins such aspropylene obtainable using as a catalyst component isopropyl (fluorenyl)(cyclopentadienyl) zirconium dichloride. Syndiotacticity, as measured bythe amount of syndiotactic pentads, rrrr was found to be 73-80%.

EP-A-577581 discloses the production of syndiotactic polypropylenesusing metallocene catalysts which have fluorenyl groups substituted inpositions 2 and 7 and an unsubstituted cyclopentadienyl ring.

EP-A-0419677 describes the production of syndiotactic polypropylene withan object to produce resin compositions having high stiffness whenmoulded. Metallocene catalysts such asisopropyl(cyclopentadienyl-1-fluorenyl) zirconium dichloride were usedin the production of the polypropylene. However the molecular weight,melting point and syndiotacticity of these products would generally berelatively low. Moreover, in certain applications where crystallinityand crystallisation rate of the desired resins are critical, thesecatalysts are not suitable.

Accordingly, there is a need to provide polyolefins, such aspolypropylenes, with improved physical properties.

SUMMARY OF THE INVENTION

The present invention aims to overcome the disadvantages of the priorart.

In a first aspect, the present invention provides use of a metallocenecatalyst component for the preparation of a syndiotactic polyolefinhaving a monomer length of up to C10, which component has the generalformula:

R″(C_(p)R₁R₂)(C_(p)′R₁′R₂′)MQ₂  (I)

wherein C_(p) is a cyclopentadienyl ring; C_(p)′ is a 3,6 di substitutedfluorenyl ring; R₁ and R₂ are each independently H or a substituent onthe cyclopentadienyl ring which is proximal to the bridge, whichproximal substituent is linear hydrocarbyl of from 1 to 20 carbon atomsor a group of the formula XR*₃ containing up to 7 carbon atoms in whichX is chosen from Group IVA, and each R* is the same or different andchosen from hydrogen or alkyl; R₁′ and R₂′ are each independentlysubstituent groups on the fluorenyl ring, each of which is a group ofthe formula AR′″₃, in which A is chosen from Group IVA, and each R′″ isindependently hydrogen or a hydrocarbyl having 1 to 20 carbon atoms; Mis a Group IVB transition metal or vanadium; each Q is hydrocarbylhaving 1 to 20 carbon atoms or is a halogen; R″ is a structural bridgeimparting stereorigidity to the component and comprises the moietyTR_(a)R_(b), in which T is chosen from group IVA, and each of R_(a) andR_(b) is independently (i) substituted or unsubstituted aryl linked to Tdirectly or by C₁-C₄ alkylene; or (ii) H.

Polyolefins produced using the metallocene catalyst component of thepresent invention are surprisingly found to have both very goodmicrotacticity, especially as determined by pentad distribution levelsin 13C nmr, and high weight average molecular weight, typically inexcess of 500,000.

Without wishing to be bound by theory, it is thought that thecombination in the present invention of an aromatic or hydrogensubstituent on the bridge of the metallocene catalyst, in combinationwith disubstitution in positions 3 and 6 of the fluorenyl ring maycontribute to an increase in the molecular weight, tacticity andcrystallinity of the polymers, leading to improved mechanical propertiesof the final product.

The applicants have unexpectedly found that if in the metallocenecatalysts the above substituent groups are present on the bridge and thefluorenyl ring is substituted in position 3 and 6, there is asignificant improvement in the qualities of the produced polymer.Increases in microtacticity, melting point and molecular weight are allobtainable with these catalysts.

According to the present invention, the fluorenyl ring may besubstituted by radicals of general formula: AR′″3 where A is preferablycarbon or silicon and is more preferably carbon. Where A is carbon, AR′″may be a hydrocarbyl selected from alkyl, aryl, alkenyl, alkyl aryl oraryl alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,amyl, isoamyl; hexyl, heptyl, octyl, nonyl, decyl, cetyl or phenyl.Where A is silicon, AR′″3 may be Si(CH3)3. Preferably at least one ofR′₁ and R′₂ is t-butyl. It is preferred that R′₁ and R′₂ are as similaras possible. More preferably both R′₁ and R′₂ are the same.

The structural bridge R″ comprises the moiety TR_(a)R_(b) in which T isdirectly or indirectly linked to Cp and Cp′. T may be indirectly linkedto each of Cp and Cp′ by C₁ to C₄ alkylene but it is preferred that T isC or Si linked directly to the two Cp rings. Where R_(a) and/or R_(b) isaryl, each aryl may be substituted or unsubstituted and may beheteroaryl. Preferred aryl groups include substituted or unsubstitutedphenyl, naphthyl and anthracyl. R_(a) and R_(b) are preferably the same.Most preferably, R″ is diphenylmethylidene.

M is preferably from Group IVB and may be hafnium, titanium or, mostpreferably, zironium. Q may be a hydrocarbyl such as alkyl, aryl,alkenyl, alkylaryl or aryl alkyl, preferably methyl, ethyl, propyl,isopropyl, butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, octyl, nonyl,decyl, cetyl or phenyl. Q is preferably a halogen.

In the proximal substituent groups R1 and R2, X is preferably C or Si.R* is preferably H. It is preferred that R1 and R2 are the same.

R₁ and R₂ should each be sufficiently small as not to interfere withsyndiotactic polyolefin production. Whilst linear hydrocarbylsubstituents of up to 20 carbon atoms may be tolerated, it is preferredthat R₁ and R₂ each have no more than 7 carbon atoms. With non-linearsubstituents each R*₃ is preferably no larger than methyl. X ispreferably C or Si. It is particularly preferred that at least one andmost preferably both of R₁ and R₂ are hydrogen. In this way, productionof syndiotactic polyolefin is favoured.

Production of syndiotactic polyolefin is particularly favoured when thesubstituent groups in the metallocene molecule are chosen so that themolecule has C_(s) symmetry or near C_(s) symmetry. The closer to C_(s)symmetry, the more favoured is syndiotactic polyolefin production.Accordingly, identity or near identity is preferred between the pairs ofsubstituents; R′₁ and R′₂, R_(a) and R_(b), and R₁ and R₂.

In a further aspect, a catalyst system is used for preparing thepolyolefins, which system comprises (a) a catalyst component as definedabove; and (b) an aluminium- or boron-containing cocatalyst capable ofactivating the catalyst component. Suitable aluminium-containingcocatalysts comprise an alumoxane, an alkyl aluminium and/or a Lewisacid.

The alumoxanes usable in the process of the present invention are wellknown and preferably comprise oligomeric linear and/or cyclic alkylalumoxanes represented by the formula:

for oligomeric, linear alumoxanes and

for oligomeric, cyclic alumoxane,

wherein n is 1-40, preferably 10-20, m is 3-40, preferably 3-20 and R isa C1-C8 alkyl group and preferably methyl. Generally, in the preparationof alumoxanes from, for example, aluminium trimethyl and water, amixture of linear and cyclic compounds is obtained.

Suitable boron-containing cocatalysts may comprise a triphenylcarbeniumboronate such as tetrakis-pentafluorophenyl-borato-triphenylcarbenium asdescribed in EP-A-0427696, or those of the general formula [L′-H]+[B Ar1Ar2 X3 X4]— as described in EP-A-0277004 (page 6, line 30 to page 7,line 7).

The catalyst system may be employed in a solution polymerisationprocess, which is homogeneous, or a slurry process, which isheterogeneous. In a solution process, typical solvents includehydrocarbons with 4 to 7 carbon atoms such as heptane, toluene orcyclohexane. In a slurry process it is necessary to immobilise thecatalyst system on an inert support, particularly a porous solid supportsuch as talc, inorganic oxides and resinous support materials such aspolyolefin. Preferably, the support material is an inorganic oxide inits finally divided form.

Suitable inorganic oxide materials which are desirably employed inaccordance with this invention include Group 2 a, 3 a, 4 a or 4 b metaloxides such as silica, alumina and mixtures thereof. Other inorganicoxides that may be employed either alone or in combination with thesilica, or alumina are magnesia, titania, zirconia, and the like. Othersuitable support materials, however, can be employed, for example,finely divided functionalized polyolefins such as finely dividedpolyethylene.

Preferably, the support is a silica having a surface area comprisedbetween 200 and 1000 m2/g and a pore volume comprised between 0.5 and 3ml/g.

The amount of alumoxane and metallocenes usefully employed in thepreparation of the solid support catalyst can vary over a wide range.Preferably the aluminium to transition metal mole ratio is in the rangebetween 1:1 and 100:1, preferably in the range 5:1 and 50:1.

The order of addition of the metallocenes and alumoxane to the supportmaterial can vary. In accordance with a preferred embodiment of thepresent invention alumoxane dissolved in a suitable inert hydrocarbonsolvent is added to the support material slurried in the same or othersuitable hydrocarbon liquid and thereafter a mixture of the metallocenecatalyst component is added to the slurry.

Preferred solvents include mineral oils and the various hydrocarbonswhich are liquid at reaction temperature and which do not react with theindividual ingredients. Illustrative examples of the useful solventsinclude the alkanes such as pentane, iso-pentane, hexane, heptane,octane and nonane; cycloalkanes such as cyclopentane and cyclohexane,and aromatics such as benzene, toluene, ethylbenzene and diethylbenzene.

Preferably the support material is slurried in toluene and themetallocene and alumoxane are dissolved in toluene prior to addition tothe support material.

In a further aspect, the present invention provides use of a catalystcomponent as defined above and a cocatalyst which activates the catalystcomponent, for the preparation of polyolefins, preferablypolypropylenes.

In a further aspect, the present invention provides a process forpreparing polyolefins, especially polypropylenes, which comprisescontacting a catalyst system as defined above with at least one olefin,preferably propylene, in a reaction zone under polymerisationconditions.

The catalyst component may be prepared by any suitable method known inthe art. Generally, the preparation of the catalyst component comprisesforming and isolating bridged substituted or unsubstitutedcyclopentadienyl, which are then reacted with a halogenated metal toform the bridged metallocene catalyst.

In one embodiment, the process for preparing the bridged metallocenecatalyst components comprises contacting the symmetrically substitutedcyclopentadiene with a substituted fluorene under reaction conditionssufficient to produce a bridged Cp-fluorenyl. The process furthercomprises contacting the bridged Cp-fluorenyl with a metal compound ofthe formula MQk as defined above under reaction conditions sufficient tocomplex the bridged Cp-fluorenyl to produce a bridged metallocenewherein M and Q are each defined as above and O≦k≦4. The process step ofcontacting the bridged Cp-fluorenyl with a metal compound can beperformed in a chlorinated solvent. The above process may also becarried out in the reverse order.

In a further embodiment, the process comprises contacting thecyclopentadiene with an alkyl silyl chloride of the formula R⁻² Si Hal₂wherein R˜ is a hydrocarbyl having 1 to 20 carbon atoms and Hal is ahalogen. An equivalent of a substituted fluorene is added to produce asilicon bridged cyclopentadienyl-substituent fluorenyl ligand. Thesubsequent steps are similar to those above for producing a bridgedsubstituted cyclopentadienyl-fluroenyl ligand coordinated to metals suchas Zr, Hf and Ti. Again, the process may also be carried out in thereverse order.

In a further embodiment, the process comprises contacting thesubstituted cyclopentadiene with a fulvene producing agent such asacetone to produce a substituted fulvene. Subsequently, in a secondstep, the fulvene is reacted with a fluorene substituted in position 3and 6, to produce a carbon bridged substitutedcyclopentadienyl-fluorenyl ligand that will produce the desiredmetallocene catalysts after reacting with MCl4, in which M is Zr, Hf orTi.

In a further aspect, the present invention provides a syndiotacticpolyolefin having a monomer length of up to C10 and a pentaddistribution (rrrr) typically comprising greater than 90%,advantageously at least 91.5%, more preferably at least 94%, andtypically up to at least 98%.

The molecular weight (Mw) of the polyolefin is typically greater than500,000, preferably at least 800,000, and typically up to at least1,500,000 or 2,000,000.

The melting point of the polyolefin is typically at least 142° C.,preferably at least 145° C., more preferably at least 149° C. and maytypically be up to 165° C.

The invention will now be described in further detail, by way of exampleonly, with reference to the attached drawings in which:

FIG. 1 shows an illustration of the structure of preferred catalystcomponents of the present invention; and

FIGS. 2 to 4 show respectively views from the top, front and side of aparticularly preferred catalyst component.

EXAMPLE 1

A. Preparation of 2,2diphenyl-[(cyclopentadienyl)-(3,6-di-tertbutyl-fluorenyl)]-methyleneReaction

Procedure

1.5 g (5.387 mmol) of 3,6-d-t-Bu-Flu in 100 ml of dry tetrahydrofuran,is placed into a 250 ml flask, under N2 and the solution is pre-cooledto 0° C. The 3,6-d-t-Bu-Flu may be synthesised according to ShojiKajigaeshi et al. Bull. Chem. Soc. Jpn. 59, 97-103(1986) or M Bruch etal. Liebigs Ann. Chem. 1976, 74-88. Then, a solution of 3.4 ml (5.387mmol) of methyllithium is added drop wise to the solution. The solutionis red and is further continued at room temperature during 4 hours.After that, a solution of 1.2407 g (5.387 mmol) of 6,6 diphenylfulvenein 10 ml of dry tetrahydrofuran is added dropwise to this solution. Thereaction is further continued during 24 hours. After adding 40 ml ofsaturated solution of NH4Cl in water, the yellow organic phase isseparated and dried with MgSO4 anhydrous. The evaporation of the solventleads to the isolation of 2.36 g (yield, 96.32%) of orange solidproduct.

B. Preparation of diphenylmethylidene[(cyclopentadienyl)-(3,6-di-tertbutyl-fluorenyl)]zirconium dichloride(1) Reaction

Procedure

2 g (4.398 mmol) of ligand is dissolved in 100 ml of dry tetrahydrofuranunder N2, and the solution is pre-cooled to 0° C. A solution of 5.5 ml(8.796 mmol) of methyllithium (1.6 mol/diethyl ether) is added dropwiseto this solution. After 3 hours, the solvent is removed in vacuum, thered powder is washed with 2×100 ml of pentane. The red dianion ligandand 100 ml of pentane are placed into a 250 ml flask, under N2. 1.02 g(4.398 mmol) of zirconium tetrachloride is added to this suspension. Thereaction mixture is red-brown and stirred overnight in a glove box.After filtration, the orange solution is removed in vacuo at 40° C. andyielded 2.3 g (85.18%) of orange powder. Apparently, this metallocene issoluble in pentane.

EXAMPLE 2 (COMPARATIVE)

Preparation of isopropylidene[(cyclopentadienyl)-(3,6-di-tertbutyl-fluorenyl)]zirconium dichloride

The synthetic procedure according to Example 1 is followed except thatthe ligand in step B is replaced by the2,2-[(cyclopentadienyl)-(3,6-di-tertbutyl-fluorenyl)]-propane.

A. Preparation of2,2-[(cyclopentadienyl)-(3,6-di-tertbutyl-fluorenyl)]-propane

Procedure

The preparation of this ligand is the same as that of Example 1, step A,but the 6,6 diphenylfulvene is replaced by 0.5720 g (5.387 mmol) of 6,6dimethylfulvene.

EXAMPLE 3

Polymerisation Procedures

Each polymerisation was performed in a 4 litre bench reactor with purepropylene. Polymerisation was initiated by introducing metallocene (0.5to 5 mg) precontacted with 1 ml of MAO (methylaluminoxane) (30% solutionin toluene obtained from WITCO) three minutes prior to its introductioninto the reactor.

Table 1 shows figures for production of syndiotactic polypropylene usingas a catalyst component an isopropylidene bridged Cp,3,6t-butylfluorenyl metallocene of Example 2 (comparative).

TABLE 1 Syndiotactic polypropylene made using isopropylidene bridgecatalysts Polymerisation Microtacticity temp Mw (kD) Mp° C. (rrrr) 30°C. 250 152-154 92-94% 40° C. 200 150 90-92% 60° C. 170 145 88-90% 80° C.140 142 86-88%

Table 2 also relates to a comparative example. Figures are shown forproduction of syndiotactic polypropylene using as a catalyst component adiphenylmethylene bridged Cp,2,7 t-butyl fluorenyl metallocene,according to EP-A-0577581. In this comparative example, the fluorenylring is substituted at positions 2 and 7 and not at positions 3 and 6 inaccordance with the present invention. Molecular weight and meltingpoint are lower than corresponding values obtained with the presentinvention. Microtacticity values would therefore also be lower.

TABLE 2 Syndiotactic polypropylene made using diphenylmethylidene bridgecatalysts with t-butyl substituents at positions 2 and 7 in fluorene.Polymerisation temp Mw (kD) Mp° C. 30° C. 671 144 50° C. 440 139 60° C.370 137

Table 3 relates to an example according to the invention. Figures areshown for production of syndiotactic polypropylene using as a catalystcomponent a diphenylene methylidene bridged Cp,3,6 t-butyl fluorenylmetallocene of Example 1.

TABLE 3 Syndiotactic polyproylene made using diphenylmethylidene bridgecatalysts with t-butyl substituents at positions 3 and 6 in fluorenePolymerisation Microtacticity temp Mw (kD) Mp° C. (rrrr) 0° C. 1500 16096-98% 20° C. 1000 152-154 92-94% 40° C. 800 150 90-92% 60° C. 680 14588-90% 80° C. 350 142 86-88%

In a further polymerisation experiment under the same polymerisationconditions, as above the following results were obtained using thediphenylene methylidene catalyst of Example 1:

TABLE 4 T Pol ° C. Hydrogen M12 Activity T (melt) T (recry) Mn Mw Mz Drrrr % 60 0 80,000 142.1 98.4 163,899 509,994 1,182,124 3.1 91.7 40 076,811 149.8 99.6 286,075 809,729 1,892,027 2.8 94.1

What is claimed is:
 1. A process for preparing a syndiotactic polyolefinhaving a monomer length of up C₁₀ which comprises: (a) contacting: 1) ametallocene catalyst component having the general formula:R″(C_(p)R₁R₂)(C_(p)′R₁′R₂′)MQ₂  wherein Cp is a cyclopentadienyl ring;Cp′ is a 3,6 di substituted fluorenyl ring; R¹ and R² are eachindependently H or a substituent on the cyclopentadienyl ring which isproximal to the bridge, provided that at least one of R₁ and R₂ is aproximal substituent, which proximal substituent is linear hydrocarbylgroup of from 1 to 20 carbon atoms or a group of the formula XR*₃containing up to 7 carbon atoms in which X is chosen from Group IVA, andeach R* is the same or different and chosen from hydrogen or an alkylgroup; R₁ and R₂ are each independently substituent groups on thefluorenyl ring, each of which is a group of the formula AR′″₃ in which Ais chosen from Group IVA, and each R′″ is independently hydrogen or ahydrocarbyl group having 1 to 20 carbon atoms; M is a Group IVBtransition metal or vanadium; each Q is a hydrocarbyl group having 1 to20 carbon atoms or is a halogen; R″ is a structural bridge impartingstereorigidity to the component and comprises the moiety TRaRb, in whichT is chosen from group IVA, and each of Ra and Rb is independently (i) asubstituted or unsubstituted aryl linked to T directly or by a C₁-C₄alkylene; or (ii) H; and 2) an aluminum or boron containing co-catalystcomponent capable of activating the metallocene catalyst component; and(b) contacting the activated catalyst of subparagraph (a) with at leastone olefin in a reaction zone under polymerization conditions to form asyndiotactic polyolefin having a monomer length of up to ten carbonatoms.
 2. A process according to claim 1, wherein A is carbon orsilicon.
 3. A process according to claim 2, wherein AR′″₃ is hydrocarbylgroup having from 1 to 20 carbon atoms.
 4. A process according to claim2, wherein AR′″₃ is C(CH₃)₃.
 5. A process according to claim 1, whereinAR′″₃ is Si(CH₃)₃.
 6. A process according to claim 1, wherein R₁′ andR₂′ are the same.
 7. A process according to claim 1, wherein T is C orSi.
 8. A process according to claim 7, wherein R_(a) and R_(b) are thesame.
 9. A process according to claim 1, wherein R″ isdiphenylmethylidene.
 10. A process according to claim 9, wherein M iszirconium or titanium.
 11. A process according to claim 10, wherein Q ishalogen.
 12. A process according to claim 11, wherein R₁ and R₂ are H.13. A process according to claim 1, wherein the metallocene catalystcomponent comprises diphenylmethylidene-cyclopentadienyl 3,6 di t-butylfluorenyl ZrCl₂.
 14. A process according to claim 1, wherein thecatalyst system further promises an inert support.
 15. A processaccording to claim 1, wherein olefin is propylene.
 16. A process forpreparing a syndiotactic polyolefin by the polymerization of propylenewhich comprises: (a) contacting; 1) a metallocene catalyst having thegeneral formula R″(C_(p))(C_(p)′)MQ₂, wherein C_(p) is a acyclopentadienyl group which is substituted with at least onesubstituent which is proximal to the bridge R″, which proximalsubstituent is linear hydrocarbyl group of from 1 to 20 carbon atoms ora group of the formula XR*₃ containing up to 7 carbon atoms in which Xis chosen from Group IVA, and each R* is the same or different andchosen from hydrogen or an alkyl group; C_(p)′ is a di substitutedfluorenyl group with substituents at the 3 and 6 positions which are thesame, and which are selected from the group consisting of methyl, ethyl,propyl, isopropyl, butyl, isobutyl, tertiary butyl, amyl, isoamyl,hexyl, heptyl, octyl, nonyl, decyl, cetyl, phenyl or trimethyl silylgroup, R″ is a structural bridge imparting stereorigidity to thecomponent and is a dimethyl silyl group, a diphenyl silyl group, adiphenyl methylene group or an isopropylidene group, M is a group IVBtransition metal or vanadium and each Q is a hydrocarbyl group having 1to 20 carbon atoms or a halogen, and 2) an aluminum or boron containingco-catalyst component capable of activating the metallocene catalystcomponent; and (b) contacting the activated catalyst of subparagraph (a)with propylene in a reaction zone under polymerization conditions toform a syndiotactic propylene polymer.
 17. The process of claim 16wherein R″ is a diphenylmethylidene or an isopropylidene group.
 18. Theprocess of claim 17 wherein Q is a halogen.
 19. The process of claim 18wherein the substituents of the disubstituted fluorenyl group are phenylgroups.
 20. The process of claim 18 wherein the substituents of thedisubstituted fluorenyl group are tertiary butyl groups.
 21. The processof claim 20 wherein M is zirconium or titanium and Q is chlorine.